Mobile communication systems were developed to provide the subscribers with voice communication services on the move. With the rapid advance of technologies, the mobile communication systems have evolved to support high speed data communication services beyond the early voice-oriented services.
Recently, standardization for a Long Term Evolution (LTE) system, as one of the next-generation mobile communication systems, is underway in the 3rd Generation Partnership Project (3GPP). LTE is a technology for realizing high-speed packet-based communications with the data rate of up to 100 Mbps, which is higher than the currently available data rate, and its standardization is almost complete.
Recent studies are focused on the LTE-Advanced (LTE-A) for improving data rate with the adaptation of several new techniques to legacy LTE system. One of the representative technologies is Carrier Aggregation. Carrier aggregation is enabling terminal to use multiple downlink and uplink carriers unlike the conventional system using one downlink carrier and one uplink carrier.
Recently, one of the main issues of LTE-A is overlapping a plurality of small cells and one macro cell in the geographically same area. Through this, it is possible to obtain so-called cell splitting gain. In order to improve the throughput using the small cells, it is necessary to aggregate the small cells for the terminal entering the small cell area as quick as possible. In the case of using the current measurement method, the terminal has to continue measurement for the small cells, resulting in significant battery power consumption.